My buddy I brew with recently landed a pound of Belma hops, so we're going to brew a single-hop pale ale. It's kind of our first foray out of the "just follow the recipe" style of brewing. Pretty excited about it.

Since we've never subbed out hops in a recipe before (except for the occasional out-of-stock substitution), I was hoping somebody might help us out real quick.

My question is this: Belma's AA% is 9.8%. That's pretty close to the 8.5% bittering hop the recipe calls for, as well as 6-9.5% the internet claims Perle is (the recipe doesn't specify any other AA% other than the Nugget), but is higher than 4.5-7% the internet claims Cascade usually is. Should we just do a straight swap-out with Belma on the ones that are close? Should we alter the amount for the Cascade, since it's a little lower?

I guess the real question is: is there a general guideline for substituting hops with different AA%s?

Generally match the AAs for hops added for longer than 20 minutes. 8.5 vs 9.5 is no difference; just use the sam amount.

Hops added 20 minutes and in are added for flavor and aroma, and not bittering. Add what you think is necessary for that point. I believe the flavor of Belma is subdued. You might want to double the amount of Cascade the recipe calls for. Someone else with experience of these hops might have better advice.

With flavor and aroma hops in a hoppy beer, you can't go too far wrong with adding too many late hops (20 minutes and under).